A substantial fraction of India's 1.35 billion population currently has immunity against the coronavirus, coupled perhaps with some natural form of immunity, three eminent scientists of the country said quoting serological surveys as well as model predictions.
The scientists Rajeeva L Karandikar of Chennai Mathematical Institute, Shekhar C Mande of Council of Scientific and Industrial Research, New Delhi and M Vidyasagar of Indian Institute of Technology in Hyderabad also made a strong case for speeding up the ongoing Covid-19 vaccination campaign which gives longer protection to the disease than natural immunity or presence of antibodies from previous infections.
India has so far vaccinated a little more than one crore health and frontline workers since launching the drive on January 16 and there have been calls by the Health Ministry and experts to speed up and expand it to other sections of the population.
India plans to cover 30 crore people through the vaccination campaign by July-August this year.
"Although the current evidence is suggestive of long-lasting immune memory, the immunity afforded by the presence of antibodies might be expected to last for only several months and not longer, while T-cell mediated immunity might last longer," the scientists said in an article carried by the Indian government's official website today.
They argued that "the most reliable longer-term protection is, however, provided through vaccination."
In an apparent boost to India's indigenous vaccine – Covaxin – which has been developed from an inanimate virus, the three scientists contended that the breadth of antibody response generated by a killed virus vaccine is likely to offer greater protection against mutated viruses, compared to vaccines that generate antibodies against the spike protein.
They said the longer the virus is allowed to spread among unprotected public, the greater the opportunities for the virus to mutate into a more virulent form, and added that is all the more reason to start vaccinations with all available resources.